- (MKAnnotationView *)mapView:(MKMapView *)mapView viewForAnnotation:(id <MKAnnotation>)annotation
{
    // If it's the user location, just return nil
    if ([annotation isKindOfClass:[MKUserLocation class]])
        return nil;

    // Handle custom annotations
    if ([annotation isKindOfClass:[NAME_OF_CLASS_IMPLEMENTING_MKANNOTATION_PROTOCOL class]])
    {
        // Try to dequeue an existing annotation view first
        MKAnnotationView *annotationView = (MKAnnotationView*)[mapView dequeueReusableAnnotationViewWithIdentifier:@"AnnotationViewIdentifier"];

        if (!annotationView)
        {
            // If an existing pin view was not available, create one
            annotationView = [[MKAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:@"AnnotationViewIdentifier"];
            annotationView.canShowCallout = YES;

            // set callout
            UIButton *rightButton = [UIButton buttonWithType:UIButtonTypeDetailDisclosure];
            annotationView.rightCalloutAccessoryView = rightButton;
        }
        else
        {
            annotationView.annotation = annotation;
        }

        return annotationView;
    }

    return nil;
}